package network;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UDPEchoServer {
    private DatagramSocket socket = null;
    public  UDPEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动");
        while (true) {
            //1 读取请求并解析
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            //为了方便打印  把二进制数据转为字符串String
            String request = new String(requestPacket.getData(),0,requestPacket.getLength());

            //根据请求计算回响
            String response = this.process(request);
            //把响应写回到客户端
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),0,response.getBytes().length,requestPacket.getSocketAddress());
            socket.send(responsePacket);
            System.out.printf("[%s,%d] req = %s,resp = %s\n",requestPacket.getAddress(),requestPacket.getPort(),request,response);
        }
    }

    public String process(String request) {
        //回显服务器
        return request;
    }

    public static void main(String[] args) throws IOException {
        UDPEchoServer server = new UDPEchoServer(9090);
        server.start();
    }
}
